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O. E. SGRIBNER.

Calling and Clearing Out Circuits for Telephone Exchanges.

No. 243,312. Patented June 21,1881.

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N. PETERS. Phu'vl-ithdgmpher. Washlllglon. Dc.

UNITED STATES PATENT OEEIc CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS,ASSIGNOR TO THE WESTERN ELECTRIC MANUFACTURING COMPANY, OF SAME PLACE.

CALLING AND CLEARING-OUT CIRCUIT FOR TELEPHONE-EXCHANGES.

SPECIFICATION forming part of Letters Patent No. 243,312, dated June 21,1881.

Application filed February 24, 1881. (No model.)

To all whom it may concern:

Be it known that I, CHARLES E. SGRIBNER, of Chicago, Illinois, havediscovered certain new and useful Improvements in Calling andClearing-Out Circuits for Telephone-Exchanges, of which the following issuch a full, clear, concise, and exact description as will enable thoseskilled in the art to practice myinvention,

reference being had to the accompanyin g drawing, forming a part of thisspecification.

My invention relates to the circuits of a telephone-exchange system. Byits use the subscribers are enabled to do their own calling after theyare connected at the central office.

My improvements, as hereinafter described, may be readily adapted to anytelephone-exchange system.

The novelty of my invention consists in one or more pairs of relays, incombination with circuits and electric apparatus at the central oflice.Each pair of relays is provided with a pair of plugs andconducting-cords. There should be such a number of outfits that anysubscriber wishing a connection may not be compelled to wait for othersto get through with the outfit that they are using, as it is evidentonly one connection can be had at once through a given pair of relays.The cords of apair of plugs should be of different colorsfor example,red and blue.

In the drawing the figure represents 2. diagram of the circuits of apair of relays, A and B, and of the lines of two subscribers con-'nected through the said pair of relays.

C is the switch-board. The telephone-lines come to the central office inthe usual manner, and connect with a switch on the switch-board, or witha switch on each of the switch-boards when more than one switch-board isused. The lines may be opened or closed to ground, according to thesystem of signaling or sending in the calls.

In the drawing the telephone-lines are 0011- nected from theirrespective switches to ground through numbers of annunciators when notin use. Line a connects with jack-knife switch I), and thence by line 0through an annunciator, and to ground. Line d connects with j ack-knifeswitch 6, and thence by line f throu gh an annunciator and to ground.Let red cord g connect with armature of relay A and blue cord h of thepair branch, the branch t passing through the magnet of relay B tocontactpointk, and the other branch, I, passing through 5 5 the magnetof relay A and to ground. Contact-point m is connected thr'ough thecallingbattery to ground by line it.

The clearing-out annnunciator is placed in the local circuit of line 0.The armature p of relay B serves as a key or circuit-closer.

The magnet ofrelay A is of high resistance, preferably about ten orfifteen times as'many ohms resistance as the resistance of the magnet ofrelay B. 6

The calling subscriber S is connected with line a, and the subscriberwanted, S is connected with line d. S having notified the con traloffice in any well-known Way that he wishes to talk with S the attendantswitchman inserts the pair of plugs in their switches 12 and c, asshown. The ground-wires c audf are thus removed, and S proceeds to ringup S by sending a current along his telephoneline a. The current thussent passes through the coil of magnet of relay A, and the armature ofrelay is moved from contact-point 7a to contact-point m, and thecalling-battery is thus thrown to the telephone-line of S The adjustmentof relayAis light as compared with the adjustment of relay B, and hencethe line i is opened at 70 before the circuit of line 0 is closed by themovement of the armature of relay B. The clearing-out annunciator,therefore, is not disturbed by the current sent by S. As soon as S hearsthe call he takes down his hand-telephone and answers the call throughhis transmitter. When S and S are through talking S hangs up thehand-telephone and sends a current along his telephone-line d. 0 Thiscurrent will all pass through the coil of the magnet of relay B, butonly a small part of this current will pass through the coil of themagnet of relay A, since the resistance of the magnet of relay A is veryhigh, as compared with the resistance of the telephoneline a. Thecircuit of line 0, therefore, is closed by the movement of the armatureof relay B, and the attendant at the central office notified by theclearing-out annunciator to disconnect the switches b and e. This isdone by pulling out the pair of plugs from the said switches.

I claim- The combination of the telephone-line circuits of twosubscribers with a pair of relays, a calling-battery, and a clearing-outannunci- 5 ator, said relays being provided with contactpoints for theirarmatures, whereby the calling-battery is thrown to line, or the circuitof the clearing-out annunciator closed, substan tially as shown anddescribed.

CHARLES E. SORIBNER.

Witnesses:

SAMUEL H. FIsH, CALVIN DE WOLF.

